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Volume 8, Number 7—July 2002


Time-Space Clustering of Human Brucellosis, California, 1973–1992 1

Geoffrey T. Fosgate*, Tim E. Carpenter*, Bruno B. Chomel*, James T. Case†, Emilio E. DeBess‡, and Kevin F. Reilly§
Author affiliations: *University of California, Davis, California, USA; †California Animal Health and Food Safety Laboratory, Davis, California, USA; ‡Department of Human Services, Portland, Oregon, USA; §California Department of Health Services, Sacramento, California, USA;

Main Article

Table 5

Population-adjusted Moran’s I (Ipop) analysis for spatial clustering of reported human brucellosis cases due to Brucella abortus and B. melitensis in Hispanic populations, California, 1973–1992.

Years No. of cases z-score p value Within %a Among %
B. abortusb
1973–1977 12 -0.01 0.99 96.7 3.3
1978–1982 12 4.28 <0.001 74.8 25.2
1983–1987 9 -0.47 0.64 125.4c -25.4c
1988–1992 23 0.15 0.88 108.8c -8.8c
B. melitensis
1973–1977 17 6.47 <0.001 62.4 37.6
1978–1982 48 8.77 <0.001 70.8 29.2
1983–1987 56 1.18 0.24 83.2 16.8
1988–1992 50 3.15 0.002 104.6c -4.6c

aPercentage of estimated spatial clustering attributed to cases in same counties and in adjacent counties.
bCases are reported as B. abortus or B. melitensis based on bacterial isolation or reported animal contact as cattle or goats, respectively, when bacterial isolation was not performed or species not determined.
cAll identified clustering due to cases in the same counties. Negative value for in % demonstrates dispersion of cases in adjacent counties.

Main Article

1 Preliminary results of this study were presented at the 9th Symposium of the International Society for Veterinary Epidemiology and Economics, August 6–11, 2000, Breckenridge, Colorado, USA.